Effect of Dietary Fat on Rat Liver Microsomal Enzymes and Lipid Composition.

Abstract

Dietary fat is known to influence the activities of various membrane-bound enzymes. The impact of various commonly consumed vegetable fats of India, viz., groundnut, coconut, safflower or mustard oil with varied fatty acid composition on the activities of liver microsomal membrane-bound enzymes and microsomal lipid composition was studied. In a feeding experiment, male weanling rats were fed these oils at 20g per 100g of the diet for 4 months. Liver microsomal cytochrome P-450 content was found to be significantly higher in the safflower oil-fed group and lowest in the coconut- and mustard oil-fed groups. The activity of UDP-glucuronyltransferase was highest in the mustard oil- and safflower oil-fed groups and lowest in the coconut oil-fed group and intermediary in the groundnut oil-fed group. The activity of Mg2+-ATPase was markedly lower in the safflower oil-fed group than in the rest of the groups. Na+, K+-ATPase activity was distinctly higher in the mustard oil-fed group, while Mg2+-ATPase activity was markedly higher in the groundnut oil-fed group. Further, the liver microsomes of safflower oil and mustard oil-fed groups showed higher amounts of cholesterol and phospholipids than the other two groups. However, the safflower oil group showed a higher cholesterol to phospholipid molar ratio than the other groups. Changes in cholesterol to phospholipid molar ratio as well as in fatty acid composition of the microsomal membranes could be responsible for the differences in the activities of the enzymes observed in the different groups.